Brachytherapy is a general term covering medical treatment which involves placement of radioactive sources near a diseased tissue and can involve the temporary or permanent implantation or insertion of radioactive sources into the body of a patient. The radioactive sources are located in proximity to the area of the body which is being treated. A high dose of radiation can thereby be delivered to the treatment site with relatively low doses of radiation to surrounding or intervening healthy tissue. Exemplary radioactive sources include radioactive seeds, radioactive rods and radioactive coils.
Brachytherapy has been used or proposed for use in the treatment of a variety of conditions, including arthritis and cancer. Exemplary cancers that can be treated using brachytherapy include breast, brain, liver and ovarian cancer and especially prostate cancer in men. For a specific example, treatment for prostate cancer can involve the temporary implantation of radioactive sources (e.g., rods) for a calculated period, followed by the subsequent removal of the radioactive sources. Alternatively, radioactive sources (e.g., seeds) can be permanently implanted in the patient and left to decay to an inert state over a predictable time. The use of temporary or permanent implantation depends on the isotope selected and the duration and intensity of treatment required.
Permanent implants for prostate treatment include radioisotopes with relatively short half lives and lower energies relative to temporary seeds. Exemplary permanently implantable sources include iodine-125, palladium-103 or cesium-131 as the radioisotope. The radioisotope can be encapsulated in a biocompatible casing (e.g., a titanium casing) to form a “seed” which is then implanted. Temporary implants for the treatment of prostate cancer may involve iridium-192 as the radioisotope. For temporary implants, radioactive rods are often used.
Conventional radioactive seeds are typically smooth sealed containers or capsules of a biocompatible material, e.g., titanium or stainless steel, containing a radioisotope within the sealed chamber that permits radiation to exit through the container/chamber walls. Other types of implantable radioactive sources for use in radiotherapy are radioactive rods and radioactive coils, as mentioned above.
Preferably, the implantation of radioactive sources for brachytherapy is carried out using minimally-invasive techniques such as, e.g., techniques involving hollow needles. It is possible to calculate a desired location for each radioactive source which will give the desired radiation dose profile. This can be done using knowledge of the radioisotope content of each source, the dimensions of the source, accurate knowledge of the dimensions of the tissue or tissues in relation to which the source is to be placed, plus knowledge of the position of the tissue relative to a reference point. The dimensions of tissues and organs within the body for use in such dosage calculations can be obtained prior to or during placement of the radioactive sources by using conventional diagnostic imaging techniques including X-ray imaging, magnetic resonance imaging (MRI), computed tomography (CT) imaging, fluoroscopy and ultrasound imaging.
During the placement of the radioactive sources into position, a surgeon can monitor the position of tissues such as the prostate gland using, e.g., ultrasound imaging or fluoroscopy techniques which offer the advantage of low risk and convenience to both patient and surgeon. The surgeon can also monitor the position of the relatively large needle used in implantation procedures using ultrasound or other imaging.
As mentioned above, brachytherapy typically employs hollow needles that are insertable into a patient's body, often with the assistance of a template. A typical template used to guide and/or inform the positioning of hollow needles at a surgical site can provide access to more than one hundred locations. The number of locations can be so numerous that a typical pitch between needle access points can include a pitch of 5 mm.
A hollow needle, as explained above, is used to implant radioactive sources and/or other types of treatment elements into patient tissue at a desired location and to a desired depth. Such treatment elements, which are implantable using the hollow needle, shall be collectively referred to as an implant. Such an implant can be an elongate treatment member, such as a strand that includes a plurality of radioactive sources (e.g., seeds) spaced apart from one another within a bioabsorbable material. Besides a strand, an implant can be another type of treatment member that includes a plurality of radioactive sources spaced apart from one another, such as a member formed of seeds and spacers that are frictionally or otherwise connected to one another (e.g., as described in U.S. Pat. Nos. 6,010,446 and 6,450,939, which are incorporated herein by reference). An elongate treatment member may also be made from a hollow tube that includes a plurality of seeds and spacers loaded within a bore of the tube, with the tube possibly heat shrunk around the seeds and spacers, or the ends of the tube otherwise closed. Alternatively, an implant can be a plurality of loose seeds and loose spacers axially aligned one behind the other. It is also possible that the implant be a single loose radioactive source. Other possibilities also exist, as would be appreciated by one of ordinary skill in the art. For example, an implant can include one or more radioactive rod or coil. An implant can also include one or more seed that has anchoring mechanisms, exemplary details of which are provided in commonly assigned U.S. patent application Ser. No. 11/187,411, entitled “Implants for Use in Brachytherapy and Other Radiation Therapy That Resist Migration and Rotation,” filed Jul. 22, 2005. Alternatively, the implant can be or include some other object and need not be radioactive, e.g. a spacer, a marker, or a thermal seed that gives off heat.
Various types of hollow needles can be used in brachytherapy, examples of which are shown in FIGS. 1A and 1B. A first type of needle, shown in FIG. 1A, is often referred to as an applicator needle, and is sometimes marketed under the trademark MICK® needle. Referring to FIG. 1A, an applicator needle 102a is shown as including a hollow needle 104a (also referred to as a cannula) with a blunt or un-sharpened distal end 106a, and a hub 108a positioned at a proximal end. The hub 108a, as shown, has a generally simple cylindrical shape. An exemplary length of the entire needle 102a including the hub is about 7⅞ inches (about 20 cm), with the hub 108a having a length of about 1 inch (about 2.5 cm). As shown in FIG. 1A, the hub 108a surrounds a proximal portion of the cannula 104a. A bore 110a (also referred to as a lumen) extends through the applicator needle 102a. An exemplary diameter of the bore 110a (i.e., the inner diameter of the canuula 104a) is about 0.042 inches.
When an applicator needle 102a is used in brachytherapy, a sharp stylet (not shown) is inserted through the lumen 110a of the hollow needle, so that the sharp distal end of the sharp stylet (e.g., a trocar tip) extends past the blunt distal end 106a of the applicator needle 102a. The needle 102a, with the sharp stylet point extending out its blunt distal end 106a, can then be inserted into patient tissue at a desired location, including to a desired depth. Thereafter, the sharp stylet is removed, and an implant (e.g., a strand, seeds and spacers, or combinations thereof) is loaded into the needle through the proximal end of the needle. Tweezers or the like can be used to insert a strand or other treatment member, and/or loose seeds and spacers, into the proximal end of the needle. However, this can be very difficult and time consuming due to the small inner diameter of the hollow needle. A blunt ended stylet (not shown) can then be inserted into the proximal opening of the needle 102a, until the distal end of the stylet contacts the proximal end of the treatment member (or most proximal seed or spacer). The needle can then be refracted with the stylet held in position so that the implant is deposited at a desired location.
Alternatively, an applicator device, such as a MICK® applicator, can be attached to the proximal end of the applicator needle 102a, and the applicator device can be used to dispose loose seeds (and optionally loose spacers) through the needle 102a and into patient tissue. The MICK® applicator is available from Mick Radio-Nuclear Instruments, Inc., Mount Vernon, N.Y. Details of the MICK® applicator are provided in U.S. Pat. No. 5,860,909.
Referring now to FIG. 1B, a second type of needle 102b, which shall be referred to herein as a locking hub needle for reasons that will be apparent (and sometimes referred to as a prostate seed needle, a standard needle, or a seed lock needle), includes a cannula 104b, a sharpened distal end 106b (e.g., a beveled end), and a hub 108b positioned at a proximal end. The hub 108b has an enlarged diameter with a funneled proximal portion 112, and threads 114 on an outer circumference, that may be used, e.g., to connect the hub 108b to a syringe. The funneled distal end 112 allows a more forgiving tolerance for inserting implants into a lumen 110b of the cannula 104b (if tweezers or the like are used to insert a treatment member and/or loose seeds and spacers into the proximal end of the needle). Nevertheless, even though the proximal funneled opening of needle 102b is larger then the proximal opening of needle 102a, it can still be very difficult and time consuming to load an implant into the needle 102b. 
Such needles 102b are typically plugged at the distal end with bonewax or some other plugging material, and pre-loaded with a treatment member and/or loose seeds and spacers, prior to the needle 102b being inserted into patient tissue. Alternatively, such needles 102b can be loaded (i.e., after-loaded) with a treatment member and/or loose seeds and spacers after the needle 102b is inserted into patient tissue.
An exemplary length of the entire needle 102b, including the hub, is about 8⅞ inches (about 22.5 cm). An exemplary length of the hub 108b is about 1 inch (about 2.5 inches). Here, only a portion of the hub 108a surrounds a proximal portion of the cannula 104b, so that the funneled portion 112 can have a larger diameter than the diameter of the cannula 104b. An exemplary diameter of the bore 110b (i.e., the inner diameter of the canuula 104b) is about 0.042 inches.
It has generally been difficult and time consuming for physicians to load a hollow needle (e.g., 102a or 102b) with a treatment member and/or loose seeds and spacers, especially after the needle has been inserted into patient tissue. It would be beneficial if devices and methods were provided for simplifying and expediting such procedures.